We had some decent weather this morning so I finished my 100 yard testing for a Palma load with the Berger 85.5 grain bullet. The rifle is a Barnard Model P with an ISSF/.169 freebore chamber, 30 in. long 7 twist Kreiger std. Palma barrel.
I tested five (5) groups starting from 25.2 grains N140 to 25.5 grains in .1 grain increments. I was using Winchester brass, CCI450 primers, and jumping the bullet .015. After testing up to 25.0 grains of powder I switched from the CCI-BR primer to the CCI450 thinking they would resist the higher pressure. It turns out both have the same cup thickness according to information found on this forum and I got vertical stringing in my groups that I had not seen prior to the switch. The primers were flattened but still rounded on the edges. The one round in the last group giving 2961 was a little hesitant to extract but otherwise there were no signs of excessive pressure. There may be other contributors to the stringing as I am a sling shooter and my bench technique could be improved. At 25.5 grains the load was slightly compressed. The best results for my application are as follows:
25.4 grains N140
Avg.: 2937 Extreme Spread: 41 FPS
High: 2953 Std. deviation: 16.7
Lo: 2912
5 shots
The group was almost completely vertical measuring about 1/2 inch tall
25.5 grains N140
Avg.: 2942 Extreme Spread: 29 FPS
High: 2961 Std. deviation: 11.4
Lo: 2932
5 shots
This group was rounder but noticeably larger.
The next step is to test ten shot strings at 500 yds. and later at LR. The usual words of caution apply.
Tom Alves
I tested five (5) groups starting from 25.2 grains N140 to 25.5 grains in .1 grain increments. I was using Winchester brass, CCI450 primers, and jumping the bullet .015. After testing up to 25.0 grains of powder I switched from the CCI-BR primer to the CCI450 thinking they would resist the higher pressure. It turns out both have the same cup thickness according to information found on this forum and I got vertical stringing in my groups that I had not seen prior to the switch. The primers were flattened but still rounded on the edges. The one round in the last group giving 2961 was a little hesitant to extract but otherwise there were no signs of excessive pressure. There may be other contributors to the stringing as I am a sling shooter and my bench technique could be improved. At 25.5 grains the load was slightly compressed. The best results for my application are as follows:
25.4 grains N140
Avg.: 2937 Extreme Spread: 41 FPS
High: 2953 Std. deviation: 16.7
Lo: 2912
5 shots
The group was almost completely vertical measuring about 1/2 inch tall
25.5 grains N140
Avg.: 2942 Extreme Spread: 29 FPS
High: 2961 Std. deviation: 11.4
Lo: 2932
5 shots
This group was rounder but noticeably larger.
The next step is to test ten shot strings at 500 yds. and later at LR. The usual words of caution apply.
Tom Alves
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